A data recording apparatus which uses a magnetic disk as a recording medium includes a hard disk drive (HDD). In some cases, the HDD employs a shingled magnetic recording method. In the shingled magnetic recording method, new data is recorded to overlap with a part of the data previously recorded by a write head. On the magnetic disk, a track is formed by data recorded by the write head. That is, on the magnetic disk provided in an HDD which employs the shingled magnetic recording method, a first track and a second track that overlaps with a part of the first track are included.
In the HDD, there is a case where data to be recorded is compressed and the compressed data is recorded on the magnetic disk. Therefore, the data recorded on the magnetic disk may be compressed at an arbitrary compression rate. The compressed data is read and then expanded to return to original data to be recorded.